The invention relates to a read device for reading a record carrier on which coded pictures have been recorded, which coded pictures represent pictures made up of a matrix of P rows of Q pixels, Q and P being integers, the ratio between the dimension of the pixels in a first direction and the dimension of the pixels in a second direction substantially perpendicular to the first direction being substantially unity, the read device comprising a read unit for reading the recorded coded pictures and for supplying coded pixels representing the pixels, a picture memory unit comprising a picture memory having memory locations, storage means for storing in the memory locations of the picture memory coded pixels representing the pixels, and fetching means for reading the information from the memory locations of the picture memory, the picture memory unit being adapted to supply the coded pixels in a sequence related to the sequence of receipt, the read device further comprising means for converting the supplied coded pixels into a picture information signal suitable for a picture display unit for displaying a representation of the coded picture stored in the picture memory and represented by the picture information signal.
Such a system is known, inter alia from the book "Compact Disc Interactive, a designer's overview", published by Kluwer (ISBN 9020121219). This book describes the so-called CD-I system. This system enables representations of coded pictures stored on a "Compact Disc" to be read and to be displayed on a display screen.
A problem encountered with such systems is the storage capacity required for the picture memory. With CD-I systems it is customary to store a coded picture comprising coded pixels, each representing a pixel whose ratio between the dimensions in the horizontal direction and the dimensions in the vertical direction is substantially equal to unity (1.05 for PAL and 1.19 for NTSC). When a representation of the coded picture is displayed on a standard TV set it is advisable to select the number of picture lines of the coded picture to be substantially equal to the number of picture lines on the TV display screen.
During reproduction a coded picture is read from the CD-I disc and is stored in a memory. The coded picture stored in the picture memory is then converted into a video signal suitable for the TV set. The memory locations in the picture memory are arranged in rows and columns in the customary way. For practical reasons known per se the number of rows and columns is preferably equal to a power of 2. The picture memory may then simply comprise commercially available integrated memory circuits. In view of the above-mentioned requirement as regards the number of coded picture lines and the dimensions of the memory a picture memory of 512 by 512 memory locations is required for displaying a representation on a TV set in the case that the coded picture is a picture having an aspect ratio of 2/3, as is customary in photography. Indeed, the power of 2 which is approximately equal to the number of picture lines on the display screen is 512, so that it is preferable to select 512 for the number of rows in the memory. The number of pixels per picture line then becomes equal to 768. The next power of 2 greater than 768 is 1024, so that the number of columns in the memory is preferably equal to 1024.
It is one of the objects of the invention to provide a read device which enables a memory with a smaller storage capacity to be used and which yet enables the above-mentioned requirements as regards the dimensions of the memory to be met. It is another object to realise this without any appreciable loss of picture quality on a display screen of a standard TV system.
A further object of the invention is to provide means enabling an enlarged and/or rotated representation of a coded (sub) picture to be obtained in a simple manner.